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Abstract

Fertilized soil is considered to be a major source of nitrous oxide (N2O) in the atmosphere. In a laboratory incubation experiment, emission of N2O was studied from a clay loam soil fertilized with urea alone and urea combined with nitrification inhibitors, viz. dicyandiamide (DCD) and thiosulphate, at different moisture regimes. Emission of N2O was observed from day 1 and was appreciable during the first 2 weeks and decreased subsequently. Soil at 80% max. water holding capacity (WHC) had highest total N2O-N emission followed by soil at field capacity and submergence. Total emissions from control (no N), urea, urea combined with DCD (urea–DCD) and thiosulphate (urea–thiosulphate) were 78.88, 744.39, 415.64 and 654.75 mg N2O-N kg–1 soil, respectively at 80% max. WHC, while total emissions from the corresponding treatments under submergence and at field capacity were 31.7, 298.5, 138.4, 272.8 and 54.6, 333.7, 217.8, 313.5 mg N2O-N kg–1 soil, respectively. Of the applied N, nitrogen lost through total N2O emissions was 1.06, 0.54 and 0.92% at 80% max. WHC; 0.45, 0.26 and 0.41% at field capacity and 0.43, 0.17 and 0.39% under submergence from urea, urea–DCD and urea–thiosulphate, respectively. Thus, addition of DCD reduced total N2O-N emission to the extent of 60, 41.5 and 49.4% under submergence, at field capacity and at 80% max. WHC, respectively, when compared to urea alone, while the corresponding reductions on addition of thiosulphate were 9.6, 7.2 and 13.5%.